Insect repelling/killing composition and method of use thereof

ABSTRACT

A process for the preparation of insect repelling/killing film. The process involves forming a clathrate compound of fenitrothion with cyclodextrin or a starch decomposition product containing cyclodextrin, at the same time granulating said clathrate compound into dry powder, melt-mixing said dry powder with a synthetic material, which is an olefin, soft vinyl chloride, or vinyl acetate plastic, in an amount of 0.1 to 50% (weight ratio), molding said mixture into pellets, and molding said pellets or a mixture of an appropriate amount of said pellets with a synthetic resin material in the form of film. .

This is a division of application Ser. No. 774,197, filed Sept. 9, 1985,now U.S. Pat. No. 4,636,343.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a process for the preparation of asynthetic resin film having insect repelling/killing abilities, in whichfenitrothion is used as insect repellent/killer.

2. Description of the Prior Art:

Films having insect repelling/killing abilities are used for wrappingfruits when they are transported, for wrapping clothes, or as underlayfor tatami or carpet, effectively protecting fruits or clothes frominsect damage and preventing the growth of mite under tatami or carpet.

Films having insect repelling/killing abilities can be largelyclassified into two groups, i.e. those prepared by interleaving alamination of synthetic resin sheets or paper with an insectrepellent/killer, and those prepared by applying an insectrepellent/killer on synthetic resin sheets or paper, or impregnatingthem with an insect repellent/killer.

Those prepared by interleaving a lamination with an insectrepellent/killer are limited in the reduction of its thickness, so thatit cannot be formed into thin film.

On the other hand, those prepared by applying an insecticide onsynthetic resin sheets or paper exert an insect repelling/killing effectonly in a short period because the insecticide applied on the surface ofthe substrate is directly exposed to outside. It is difficult toimpregnate synthetic resin with an insecticide, although paper can beimpregnated. It has not been attempted so far to incorporate aninsecticide with a synthetic resin material when the resin is molded andto form it into film.

Under these circumstances, it has been expected to develop a productwhich can be molded into film, in which an insecticide is incorporatedwith a synthetic resin material, characterized in that the obtained filmshows not only a homogeneous but also prolonged insect repelling/killingeffect, in such a manner that the insecticide appropriately bleed to thesurface of the film.

SUMMARY OF THE INVENTION

The process for the preparation of insect repelling/killing filmaccording to the present invention is characterized in forming aclathrate compound of fenitrothion with cyclodextrin or a starchdecomposition product containing cyclodextrin, at the same time formingsaid clathrate compound into dry powder, melt-mixing said powder with asynthetic resin material in an amount of 0.1 to 50% (weight ratio),molding said mixture into pellets, and molding said pellets or a mixtureof an appropriate amount of said pellets with a synthetic resin materialin the form of film. Formation of a clathrate compound of fenitrothion,the insect repellent/killer used in the present invention, withcyclodextrin can afford a homogeneous mixture with a synthetic resinmaterial and enables fenitrothion to appropriately bleed to the surfaceof the film when the mixture of the clathrate compound with thesynthetic resin material is molded in the form of film.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fenitrothion used in the present invention (Sumithion in brand name;manufactured by Sumitomo Chemical Co., Ltd.) is represented by thechemical name: O,O-dimethyl-O-(3-methyl-4-nitrophenyl)thiophosphate.Fenitrothion is employed as the insect repellent/killer for the presentinvention because of its excellent effect and safety due to its lowtoxicity. Also, it can be easily formed into a clathrate compound withcyclodextrin and incorporated with a synthetic resin material formolding because of its high resistance to heat.

Cyclodextrin used in the present invention is a special dextrin, inwhich D-glucose molecules are linked circularly by the α-1,4-bond, andcharacterized in a doughnut-like molecular structure with a hollowinside, the diameter of said hollow ranging from 6 to 10 Å. There arethree types of cyclodextrin, i.e. α-type, β-type, and γ-type, classifiedaccording to the number of the structural units of D-glucose. Any ofthese three types can be used in the present invention. Among them,β-cyclodextrin is in the form of white crystalline powder andrepresented by the molecular formula of (C₆ H₁₀ O₅)₇. The molecularweight is 1135 and the melting point ranges from 300° to 305° C. (dec.).

Starch decomposition products containing cyclodextrin, which can be usedinstead of cyclodextrin, can be obtained by various methods, whichinclude, for example, those obtained as the intermediate in thepreparation of cyclodextrin by the action on starch of acyclodextrin-producing enzyme formed by the microorganisms belonging togenus Bacillus. The process for the preparation of such intermediatewill be described in more detail below.

A liquid containing starch is formed into homogeneous paste, the pHvalue of which is adjusted to 10, and cooled. Cyclodextringlycosyltransferase, which is a fermentation product of a microorganismselected from among genera Bacillus No. 13, Bacillus No. 17-1, BacillusNo. 38-2, Bacillus No. 135, and Bacillus No. 169 is added to the liquidfor reaction. Said cyclodextrin glycosyltransferase has its optimum pHvalue in the alkaline range and a high-temperature stability. After theenzyme is deactivated by heating the reaction liquid, the liquid isagain cooled, the pH value being adjusted to 5.0. Commercially availableglucamylase is added to the reaction liquid to decompose the unreactedsubstances.

The reaction liquid is then filtered by an ordinary method, concentratedso that 40% or more of cyclodextrin will be contained therein, and asmall amount of cyclodextrin is added to the concentrated liquid asseed. After the liquid is left to stand, the precipitates ofcyclodextrin deposit, which will be filtered and dried, yieldingβ-cyclodextrin. The filtrate serves as the desired starch decompositionproduct containing cyclodextrin (see Japanese Patent Publication No.43897/1977).

The above-mentioned microorganism, i.e. genera Bacillus No. 13, BacillusNo. 17-1, Bacillus No. 38-2, Bacillus No. 135, and Bacillus No. 169 areall deposited with the Fermentation Research Institute of the Agency ofIndustrial Science and Technology as FERM-611, 612, 614, 617 and 618.

The products obtained by re-purifying the above-described filtrate byion-exchange resin and concentrating are commercially available as malthoney containing cyclodextrin. This malt honey can be used also in thepresent invention.

The starch decomposition products containing cyclodextrin to be used inthe present invention are not limited to those obtained by the methoddescribed above. Starch decomposition products obtained by any methodcan be used so long as they contain α, β, or γ-cyclodextrin or a mixturethereof.

The synthetic resin material to be used in the present invention musthave a low melting point, because fenitrothion is decomposed at atemperature of 180° C. or higher, though fenitrothion is said to beresistant to high temperatures. As the molding temperatures of somesynthetic resin materials are higher than 180° C., it is necessary toselect a synthetic resin material that has a molding temperature lowerthan the heat-resistant temperature of fenitrothion. Such syntheticresin materials preferable for the present invention include olefinplastics, soft vinyl chloride plastics, and vinyl acetate plastics.

The process for the preparation of insect repelling/killing film of thepresent invention will be more readily understood by the followingexamples.

EXAMPLE 1

85 parts by weight of α-cyclodextrin was added to 15 parts by weight offenitrothion, and the mixture was blended under stirring for 1 hourwhile keeping the temperature at 50° C., to prepare a clathrate compoundof fenitrothion with cyclodextrin. The obtained clathrate compound wasgranulated into powder having a particle size of 150 mesh or finer witha vacuum drier at a drying temperature of 60° C. 50 parts by weight ofthe obtained powder and 50 parts by weight of soft vinyl chloridecompound were melt-mixed, and molded into pellets by the cold cutmethod. A mixture of 10 parts by wight of the obtained pellets with 90parts by weight of the soft vinyl chloride compound was molded in theform of film by calendering.

EXAMPLE 2

90 parts by weight of β-cyclodextrin was added to 10 parts by weight offenitrothion and the mixture was blended under stirring for 1 hour whilekeeping the temperature at 50° C., to prepare a clathrate compound offenitrothion with cyclodextrin. The obtained clathrate compound wasgranulated into powder of 150 mesh or finer with a spray drier at adrying temperature of 60° C. 30 parts by weight of the obtained powderand 70 parts by weight of soft vinyl chloride compound weremelt-melt-mixed, and molded into pellets by the hot cut method. Amixture of 20 parts by weight of the obtained pellets with 80 parts byweight of polyethylene compound was molded in the form of film byextrusion molding.

EXAMPLE 3

85 parts by weight of a starch decomposition product (containing 50% ofα, β, and γ-cyclodextrin) was added to 15 parts by weight offenitrothion, and the mixture was blended under stirring for 1 hourwhile keeping the temperature at 50° C., to prepare a clathrate compoundof fenitrothion with cyclodextrin. The obtained clathrate compound wasgranulated into powder of 150 mesh or finer with a vacuum drier at adrying temperature of 60° C. 20 parts by weight of the obtained powderand 80 parts by weight of polyethylene pellets were melt-mixed, moldedinto pellets by the cold cut method, and further molded in the form offilm by calendering.

EXAMPLE 4

85 parts by weight of a starch decomposition product (containing 15% ofα, β, and γ-cyclodextrin) was added to 15 parts by weight offenitrothion, and the mixture was blended under stirring for 1 hourwhile keeping the temperature at 50° C., to prepare a clathrate compoundof fenitrothion with cyclodextrin. The obtained clathrate compound wasgranulated into powder of 150 mesh or finer with a spray drier at adrying temperature of 60° C. 10 parts by weight of the obtained powderand 90 parts by weight of polyvinyl acetate compound were melt-mixed,and molded into pellets by the underwater cut method. A mixture of 40parts by weight of the obtained pellets with 60 parts by weight of thepolyvinyl acetate compound was molded in the form of film by extrusionmolding.

EXAMPLE 5

80 parts by weight of α-cyclodextrin was added to 20 parts by weight offenitrothion and the mixture was blended under stirring for 1 hour whilekeeping the temperature at 50° C., to prepare a clathrate compound offenitrothion with cyclodextrin. The obtained clathrate compound wasgranulated into powder of 150 mesh or finer with a drum drier at adrying temperature of 60° C. 10 parts by weight of the obtained powderand 90 parts by weight of ethylene-vinyl acetate compound weremelt-mixed, and molded into pellets by the sheet cut method. The moldedproduct was further molded in the form of film by extrusion molding.

The insect repelling/killing films obtained by the processes of theabove examples all showed not only a homogeneous but prolonged insectrepelling/killing effect, because of the appropriate bleeding of theinsect repellent/killer contained therein to the surface of the film.The obtained insect repelling/killing film can be applied as follows:

APPLICATION EXAMPLE 1

The present insect repelling/killing film can be used for wrappingfruits to be transported, expecially for prolonged transportation ofbananas, oranges, or apples to be imported or exported, so that thesefruits can be protected from insect damage during the transportation.

APPLICATION EXAMPLE 2

The present insect repelling/killing film can be used for covering cutflowers or potted plants, on transportation or ornamented, to protectthem from insect damage.

APPLICATION EXAMPLE 3

Clothes to be kept for long can be protected from insect damage bywrapping them with the present insect repelling/killing film.

APPLICATION EXAMPLE 4

Tatami or carpets can be protected from mite damage by underlaying thepresent insect repelling/killing film.

APPLICATION EXAMPLE 5

The present insect repelling/killing film can be used as the lining forbags for packaging cereals, to protect them from so-called insectdamage, as the eggs of insects are killed, whereby the storage periodcan be prolonged.

As described heretofore, the present process for the preparation ofinsect repelling/killing film, which is characterized in forming aclathrate compound of fenitrothion with cyclodextrin and molding amixture of said clathrate compound with a synthetic resin material inthe form of film, enables molding of films having a homogeneous insectrepelling/killing effect because of the homogeneous dispersion of theinsect repellent/killer in the film, and also this insectrepelling/killing effect is prolonged, because the insectrepellent/killer appropriately bleeds to the surface of the film. Thestrength of the insect repelling/killing ability can be freely selectedby varying the amount of fenitrothion or the pellets incorporated independence on the types of insects. Moreover, the film having a desiredthickness can be molded, including those as thick as plate. Thus theeffect of the present insect repelling/killing film is remarkable.

We claim:
 1. An insect repelling/killing film made according to theprocess comprising preparing a clathrate compound of fenitrothion incyclodextrin, drying the clathrate compound, granulating the driedclathrate compound into a dry powder, mixing the melting the dry powderand a synthetic resin material in a weight ratio of clathrate compoundto synthetic resin material ranging from 0.1 to 4%, molding the moltenmixture into pellets and molding the pellets into a film.
 2. An insectrepelling/killing film as in claim 1, wherein the synthetic resinmaterial is selected from the group consisting of olefin plastic, softvinyl chloride plastic and vinyl acetate plastic.
 3. An insectrepelling/killing film as in claim 1, wherein the synthetic resinmaterial has a molding temperature lower than the decompositiontemperature of fenitrothion.
 4. An insect repelling/killing film as inclaim 1, wherein the clathrate compound is homogeneously dispersed inthe synthetic resin material.
 5. An insect repelling/killing film as inclaim 1, further comprising a second synthetic resin material.
 6. Aninsect repelling/killing film as in claim 5, wherein the secondsynthetic resin material is a polyethylene plastic.
 7. An insectrepelling/killing film made according to the process comprisingpreparing a clathrate compound of fenitrothion in a starch decompositionproduct containing cyclodextrin, drying the clathrate compound,granulating the dried clathrate compound into a dry powder, mixing andmelting the dry powder with a synthetic resin material in a weight ratioof clathrate compound to synthetic resin material ranging from 0.1 to4%, molding the molten mixture into pellets and molding the pellets intoa film.
 8. An insect repelling/killing film as in claim 7, wherein thesynthetic resin material is selected from the group consisting of olefinplastic, soft vinyl chloride plastic, vinyl acetate plastic andpolyethylene plastic.
 9. An insect repelling/killing film as in claim 7,wherein the synthetic resin material has a molding temperature lowerthan the decomposition temperature of fenitrothion.
 10. An insectrepelling/killing film as in claim 7, wherein the clathrate compound ishomogeneously dispersed in the synthetic resin material.
 11. An insectrepelling/killing film as in claim 7, further comprising a secondsynthetic resin material.
 12. An insect repelling/killing film as inclaim 11, wherein the second synthetic resin material is a polyethyleneplastic.